Extramedullary Leukemia in Pediatric AML

Extramedullary leukemia (EML) is a common finding in children with acute myeloid leukemia (AML) and frequent sites of EML include central nervous system (CNS), orbit, and skin. Patients with orbital EML have good outcomes due to association with the favorable genetic marker t(8;21). Patients with CNS disease generally do well with intrathecal triple therapy augmented in induction cycles, but they may still have increased risk of CNS relapse compared to patients without CNS disease. EML of the skin is associated with very young age and rearrangements of KMT2A, and these patients generally have an inferior outcome. Routine use of radiation therapy is not recommended for myeloid EML, but it may be used emergently to treat tumor compression of vital structures at initial presentation or to treat relapsed or refractory EML. Standardized AML treatment approaches with current intensive chemotherapy regimens including high dose cytarabine are appropriate for patients with myeloid EML. Presence of EML should not be used alone to determine need for stem cell transplant (SCT). Risk-adapted treatment should utilize genetic markers and disease response that includes assessment of remission in EML sites.